*2.3. X-ray Photoelectron and* Diffraction *Analysis of DLCs*

X-ray photoelectron spectroscopy (XPS) was used to study the chemical and electronic state of carbon atoms on the surface of samples with DLCs. The analysis was performed using Thermo Scientific's K-ALPHA X-ray photoelectron spectrometer (Thermo Fisher Scientific Inc., Bremen, Germany).

The samples were both shot in the initial state of the coating surface and after surface treatment for 6 min with an Ar<sup>+</sup> ion beam to remove the adsorbed layers with high carbon and oxygen content. High-resolution photography was performed using monochromatic and polychromatic Mg Kα and Al <sup>K</sup><sup>α</sup> radiation at a power of 200–300 W and a voltage of 14 kV, pressure in the chamber 7 <sup>×</sup> <sup>10</sup>−<sup>8</sup> Pa.

XPS analysis was performed for various peaks of the DLC layer within the prominent C1s peak: *sp*<sup>2</sup> and *sp*<sup>3</sup> peaks, characterizing carbon hybridization, and C=O and C–O peaks, characterizing various compounds of the components with oxygen and other elements. Besides, we analyzed the peaks of the phases containing silicon compounds in the coating. For each component of the DLC layer, the following characteristics were measured using XPS: start binding energy (Start BE), binding energy (BE), end binding energy (End BE), full width at half maximum (FWHM), and atomic percent (Atomic %).

A Panalytical Empyrean X-ray diffractometer (PANalytical, Almelo, The Netherlands) with monochromatic Cu Kα-radiation was used to study the stresses. The stresses were determined by the classical sin2ψ method with a grazing beam at a fixed angle of incidence of the beam ψ<sup>0</sup> and scanning along the 2θ axis.
